Lewis acid doped polyphenylene sulfide (PPS) films have been shown to be semiconductors under controlled conditions. That property coupled with their electrical insulating properties in the undoped form make them suitable candidates for the fabrication of semiconducting devices. However, the physical properties of PPS (e.g., its intractable nature, and poor processibility) do not allow for facile preparation of miniaturized electronic devices having intricate circuit patterns.
To address that problem polymeric sulfonium salts were prepared by phenylation of polyphenylene sulfide through the thermal decomposition of diphenyliodonium salts (The Wall Street Journal, Aug. 29, 1990, page B 1; and Chemical and Engineering News, Sep. 10, 1990, page 26), and PCT published patent application WO 92/04396 (Internat. Appl. No. PCT/US91/05301). It was reported that, on photolysis under inert atmosphere, those polymeric sulfonium salts formed black metallic semiconducting polyphenylene sulfide. The method used to prepare those sulfonium salts involves reaction with polyphenylene sulfide which, as mentioned above, is an intractable polymer having limited solubility at temperatures below 200.degree. C. Further, though the specific stoichiometry of the polymers in the art is unknown, the method used to prepare them would lead to random placement of the sulfonium salt centers along the polymer backbone.
Nucleophilic aromatic substitution has been used for studied for many years as a way to prepare aromatic compounds including polymers such as PPS (for example, see Meisenheimer, J. Ann. 1901, 323, 205; Strauss, M. J. Accts. Chem. Res. 1974, 7, 181; Ho, K. C.; Miller, J.; Wong, K. W. J. Chem. Soc. B 1966, 310). Generally, the reaction is best carried out in a polar aprotic solvent at elevated temperature (i.e., &gt;150.degree. C.) in order to provide a reasonable reaction rate.
U.S. Pat. No. 4,954,416 and the cited references disclose the reaction of fluorinated arylsulfonium salts with nucleophiles such as amines with production of hydrogen fluoride.
U.S. Pat. No. 4,954,416 and the cited references disclose the reaction of fluorinated arylsulfonium salts with nucleophiles such as amines with production of hydrogen fluoride.
The reaction of a methyl(trimethylsilyl)benzotriazole with aryl fluorides in N,N-dimethylformamide (a polar aprotic solvent was disclosed by Rudyk, V. I.; Troitskaya, V. I.; Yagupol'skii, L. M. Zh. Org. Khim. 1980, 16(12), 2624-5.
When combined with the reported organic solvent solubility of the polymeric sulfonium salt, this technology appears to provide a route to solvent coatable, photoimageable semiconducting polymers for microelectronic applications. Additionally, the polymeric sulfonium salts of the present invention are useful as photoinitiators for cationic and free-radical curing applications.